Vulnerability Scanning

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1. Continuous Vulnerability Scanning

Purpose: To identify and remediate vulnerabilities in your environment before attackers can exploit them.

• Why: Cybercriminals actively scan for unpatched systems and known vulnerabilities to gain unauthorized access. Continuous vulnerability scanning ensures that you are aware of potential weaknesses in your environment.

• Technical Example:

  • Automate Vulnerability Scanning:

    • Use tools like Nessus, Qualys, or OpenVAS to perform automated vulnerability scans:

      • Schedule daily or weekly scans using the tool's interface or API.

      • Example Nessus API command to initiate a scan:

        curl -X POST -H "X-ApiKeys: accessKey=YOUR_ACCESS_KEY; secretKey=YOUR_SECRET_KEY" https://<NESSUS_SERVER>:8834/scans

    • Configure the scanner to prioritize high and critical vulnerabilities:

      • Set severity thresholds in the scanning tool to focus on vulnerabilities with CVSS scores of 7.0 or higher.

  • Integrate with SIEM for Real-Time Alerts:

    • Send scan results to a Security Information and Event Management (SIEM) system like Splunk or QRadar for real-time monitoring:

      • Example Splunk configuration to ingest Nessus scan data:

        [monitor:///path/to/nessus/reports]
        sourcetype = nessus_scan

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2. Remediation of High and Critical Vulnerabilities

Purpose: To address vulnerabilities that pose the greatest risk to your environment.

• Why: While not all vulnerabilities can be patched immediately, high and critical vulnerabilities must be prioritized due to their potential impact.

• Technical Example:

  • Patch Management:

    • Use patch management tools like WSUS (Windows Server Update Services) or SCCM (System Center Configuration Manager) to deploy patches:

      • Example WSUS PowerShell command to approve updates:

        Approve-WsusUpdate -Update (Get-WsusUpdate -Classification "Critical Updates") -Action Install -TargetGroupName "All Computers"

    • For Linux systems, use package managers like yum or apt to apply patches:

      sudo yum update --security

  • Manual Remediation:

    • If patches cannot be applied immediately, document and mitigate risks manually:

      • Example: Disable vulnerable services or ports until patches are available.

        systemctl stop <vulnerable_service>

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3. Network Segmentation for Vulnerable Systems

Purpose: To isolate systems that cannot be patched immediately, reducing the risk of exploitation.

• Why: If a system cannot be patched due to compatibility issues or operational constraints, network segmentation limits its exposure to potential attackers.

• Technical Example:

  • Segment Vulnerable Systems:

    • Place vulnerable systems in a separate VLAN or subnet:

      vlan 20
      name VulnerableSystems
      exit
      interface GigabitEthernet0/2
      switchport access vlan 20

    • Restrict traffic to and from the segmented network using firewall rules:

      access-list 120 deny ip any 192.168.20.0 0.0.0.255
      access-list 120 permit ip any any

  • Use Host-Based Firewalls:

    • Configure host-based firewalls to block unnecessary inbound and outbound traffic:

      New-NetFirewallRule -DisplayName "Block Vulnerable Port" -Direction Inbound -LocalPort 445 -Protocol TCP -Action Block

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Conclusion

Continuous vulnerability scanning is a critical component of a robust cybersecurity strategy. By automating scans, prioritizing high and critical vulnerabilities, and applying patches promptly, organizations can reduce their attack surface significantly. For systems that cannot be patched immediately, network segmentation provides an additional layer of protection by isolating vulnerable assets.